It is common in gauges made of metal, as they are for instance used in connection with a Bourdon tube for measuring and indicating pressure or temperature, to fix the spiral spring used for resetting the pointer shaft by providing a transverse bore in a spacer shaft of the gauge or in an additional shaft specifically provided for this purpose, threading the outer end of the spiral spring into this bore, and wedging it therein by means of a usually conical pin.
In another known variation, a spacer column of the gauge is provided with a radial groove instead of the transverse bore, and the outer end of the spiral spring is caulked in the groove.
Further variations are known in which the end of the spiral spring is welded or glued to a spacer column.
It is a common drawback of all known gauges that they require a separate step in the manufacturing process for fixing the outer end of the spiral spring. Particularly in high-response gauges employing very fine spiral springs, this process step is cumbersome and causes a relatively high reject rate. In addition, in the known gauges, the outer end of the spiral spring can be fixed only after the gauge has been assembled, which excludes economic automation.
It is an object of the invention to devise a gauge of the above-mentioned type in such a manner that the previously required additional step of the manufacturing process for positioning the outer end of the spiral spring is saved.
It is another object of the invention to provide a gauge in which the spiral spring is mounted in a completely tension-free manner at least until the assembly of the gauge has been completed.
It is a further object of the invention to provide a gauge in which a secure fixing of the spring end is achieved during the normal process of assembling the gauge without additional structural provisions or additional manufacturing steps.
It is another object of the invention to provide a gauge which allows the tension and position of the spiral spring to be adjusted upon completion of the assembling process.